This proposal aims to develop combined immunocytochemistry and immunoautoradiography for localizing neuroactive substances and their associated enzymes within the nerve cells of the cerebellum and the raphe nuclei at both light and electron microscopic levels. With these methods the coexistence within single neurons of multiple neuroactive agents, such as serotonin and peptides, or gamma aminobutyric acid and peptides, will be examined. Methods will be developed for tracing the chemically specific pathways in the brain by the use of two differentially marked polyclonal or monoclonal antibodies placed in vivo by microinjections. Such methods for discovering the paths and connections of neurons with multiple neuroactive agents based upon tracing of their individual chemical signatures will provide increasingly sophisticated tools for gaining additional insight into the chemical and structural organization of the nervous system. A developmental study will be made in the cerebellum of the acquisition of neuroactive substances in Purkinje cells. The models to be used here, the cerebellar GABA neurons and the serotonin raphe neurons, have been implicated in th control of motor disorders, such as Parkinson's disease, various ataxias and in schizophrenia, depression, sleep disorders, and cerebro-vascular disorders.